Recently, with miniaturization, reduction in weight and sophistication of electronic devices, refinement and multilayering of copper wiring have been strongly desired for printed-wiring boards.
A semi-additive process is one of production methods for forming a micro wiring. According to this method for forming a wiring, a metal layer called a seed layer is formed on an insulation material (as the metal layer, a chemical copper plating is generally used), a plating resist layer is formed on the surface thereof, and after that, exposure and development are performed to form a resist pattern. After that, an electrolytic copper plating is provided, the resist is stripped, and the seed layer is removed by etching to form a copper wiring.
As copper etching solutions for the semi-additive process, for example, an etching solution containing hydrogen peroxide, sulfuric acid, azoles and bromine ion (Patent Document 1), an etching agent comprising sulfuric acid, hydrogen peroxide and a benzotriazole derivative (Patent Document 2) and an etching solution comprising hydrogen peroxide and sulfuric acid as the main components and azoles as additives (Patent Document 3) are disclosed, and as copper etching solutions, for example, an etching solution containing hydrogen peroxide, sulfuric acid, aminotetrazole and phenylurea (Patent Document 4), an etching solution containing hydrogen peroxide, mineral acid, azoles, silver ion and halogen (Patent Document 5) and an etching solution containing hydrogen peroxide, sulfuric acid, benzotriazoles and chloride ion (Patent Document 6) are disclosed.
Recently, the width of copper wiring has been decreased from conventional 10-20 μm to less than 10 μm, and moreover, decrease to several μm has been studied for next-generation products. Since the dissolution rate of a chemical copper plating is not higher than the dissolution rate of an electrolytic copper plating when using a conventional etching solution, the width of copper wiring has been significantly decreased. Alternatively, when the dissolution rate of a chemical copper plating is extremely higher than the dissolution rate of an electrolytic copper plating, excessive dissolution of the chemical copper plating portion, so-called undercut occurs to cause disappearance of wiring. Therefore, it is difficult to form a micro wiring by means of a semi-additive process.